Study objectives-To evaluate the feasibility ofa novel approach to measure compliance of sentinel general practitioners (SGPs) in sentinel public health surveillance and to determine the characteristics in the SGP's profile that can be objectively associated with their perseverance in public health surveillance.

Design-Prospective study of the compliance of the SGPs (compliance being defined as the length of time during which an SGP complies with a given theoretical surveillance protocol) and qualitative study of the determinants of their initial motivations (using group and face to face interviews).

Setting-The 1970 SGPs who have participated in the Sentinel system since 1984.

Participants-Among them, the 502 SGPs recruited since 1 July 1992 have been questioned by mailed questionnaire and 20 SGPs have been questioned during face to face semistructured interviews.

Main results-According to the maximum number of silences allowed by the given theoretical protocol, median compliances varied between 1.9 months (95% CI= (1.8,2.0)) and 14.3 months (95% CI= (13.8,15.2)). In multivariate analysis, long compliances for SGPs with a <=5 or 320 years seniority was seen and an interest in using multimedia home servers.

On the other hand, interest in local epidemiological surveys and previous experience with other surveillance networks or clinical trials were associated with short compliances. (...)